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In the previous post we talked about Darcs 2.8's read-only support for old-fashioned (OF) repositories. This reduced support will help us simplify the code base and focus on new features and optimizations for the Hashed repositories, that are now the recommended way to use Darcs.

New features

Let us review the features that were not in 2.5 and that we are working on now:

rebase: this is a long-wanted Git feature that may be merged into Darcs 2.8. It is currently maintained on a separate branch. We will be confident to include it in the 2.8 release if we are sure we get the UI right by then. We already had some feedback but if you want to try it please go ahead and tell us what you think.

Hence to start hacking on a project hosted like this, you need to wait as long as the history of the project is large. This is only bearable for small histories. For instance, the Xmonad repository (>1100 patches) can take up to 7 minutes to be retrieved on an ADSL line, while the repositoy itself is only 5 MBytes big.

On the other hand, when getting a Hashed repository, Darcs does:

get pristine file 0, get pristine file 1, ..., get pristine filem

get patch n, get patch n-1, ... , get patch 0

build local working directory tree

Step 2. can be skipped with the --lazy flag, or can be interrupted by hitting CTRL-C. This is fine, since the new local repo has the address of the remote repo and Darcs can fetch patches on demand. Hence, the wait can be reduced a lot, and dowloading with --lazy is as long as the working copy is large. The Xmonad repository has about 30 pristine files, weighting less than 200 KBytes, so getting those would only be a matter of seconds.

By the way, getting a Darcs repo with--lazy is strictly more powerful than doing a checkout of a Subversion repository: even though you don't have patches locally, you have the high-level history of the project (i.e., you can use darcs changes offline). However, looking into the patch contents (darcs changes -v) does require you to access the remote repository.

Darcs 2.8 will contain a new optimization called packs. Running the command darcs optimize --http in a repository will store a pack of the pristine and a pack of the patches inside of it. Packs are basically tar.gz archives. Darcs will detect these packs when doing a get and act as follows:

get pristine pack

get missing pristine files

get patches pack

get missing patches

build working directory tree

Steps 1. and 3. consist in transferring a single file via HTTP, which is much faster than transferring many little files. Steps 3. and 4. are skipped if the flag --lazy is used.

You need to run darcs optimize --http manually on the public repository of your project from time to time, as this will not happen automatically. The best moment to do that is after pushing a tag, since this enables people who use get --tag X (with X being the last tag) to take advantage of the optimization.

Conclusion

This is probably not going to be the only new features that we will try to fit into the 2.8 release, so when we have more we will let you know. Before May 2011 we are going to try to release feature-based alpha versions of Darcs. They will be called Darcs 2.7.x and will be for users who want to try out bleeding-edge features and give us feedback.

If you can't wait, you can simply build the current Darcs HEAD with darcs get --lazy http://darcs.net and cabal update && cabal install -f-library inside of the obtained directory.

EDIT: removed darcs-fastconvert from the list since as of now this is not a supported feature of Darcs.

Tuesday, November 23, 2010

A month ago, we released Darcs 2.5. This version brought performance improvements and a few nice features like trackdown --bisect and UTF8 patch metadata. Since we follow a time-based release schedule, Darcs 2.8, the next major release, will be released in May 2011, and we are at the beginning of the work that will be part of it. So what are we working on now?

One of the hot topics of Darcs 2.8 will be repository formats. As of now, Darcs can work with two kinds of repositories: the old-fashioned (OF) ones and the Hashed ones. OF has been around since the very first Darcs, while the Hashed format has been introduced in Darcs 2.0 in April 2008.

Why Hashed

The reasons why the Hashed format was introduced were robustness and performance.

To understand robustness, one has to know that darcs repositories contains patches (of course), but also a "pristine cache" which is the latest recorded state of the files stored in the repository. It can be rebuilt from the patches of the repository, so it is not really mandatory in theory, however it makes some commands run in reasonable time. The command whatsnew, for instance, show the current unrecorded modifications in your working copy, and works by comparing your working copy with the pristine.

In OF repositories, the pristine directory is simply a plain filesystem tree. The consequences are that if an external program (say Subversion or Unison) adds files to that directory, Darcs will believe they really belong to the pristine cache! Hence, the command whatsnew would tell that you are missing some file in your working copy, and the command record would record a wrong patch! More generally, OF repositories can not be really checked for integrity: Darcs can not know you modified a pristine file by hand.

In Hashed repositories, the pristine is a directory containing files named by the SHA1 hash of their contents, and there is a special file that tells the hash of the root directory of the pristine. Hence, adding bogus files to the pristine directory is harmless: they will never be read. So bring on all your Subversions, Unisons and Dropboxes: Darcs can not longer be tricked.

There is another downside of OF: getting them via HTTP is very slow. Indeed, they contain no list of pristine files. You can not directly copy the remote pristine files in order to get a working copy. So you need to get all the patches, and then locally rebuild a pristine and a working copy, making the delay until getting a working copy linear in the history of the project. On the other hand, the latest working copy of a Hashed repo can be obtained with darcs get --lazy, which does not need to retrieve the history of the project.

The developers are not amused

Those are downsides of OF for users. But we, as developers, are also not very pleased with some parts of the Darcs codebase. The code that handles repositories is not really greatand lacks modularity. Moreover, nobody is really motivated to maintain code for OF, since we know Hashed repositories are better and there is ongoing work in order to make Darcs more performant with them. For instance, the work done in Summer of Code 2009 has then been incorporated in Darcs 2.4 and has boosted performance of Darcs a lot. In Darcs 2.5, performance of commands like record and pull have been substantially improved. None of these changes concern OF repositories.

Hence we have decided to stop struggling with old code, and from Darcs 2.8, only read-only access will be provided for OF repositories. This means you will still be able to use the commands get, pull and send to interact with remote OF repositories. On the other hand writing in an OF repository with record, pull or apply will no longer work, and commands that rely on the pristine files, like whatsnew, diff or dist, will also fail. We will make sure the user interface will remain clear and helpful in those cases.

For us, this is a step further towards simplify the code base and make it generally more modular. This will help usfocussing on performance improvement for the Hashed format and modern features for the Darcs client without having to think about OF maintenance.

Should it concern you?

Switching to Hashed repositories has a drawback: Darcs 1 binaries do not know how to interact with them. If you manage a project whose source code is hosted in a Darcs repository, then you should ensure that all contributors use a Darcs 2 binary (darcs --version).

For the record, Darcs 2.0 was released in April 2008 and is now adopted in most current versions of the major Linux distributions. The release of Darcs 2.8 is planned for May 2011, so no problematic situation due to OF deprecation will happen before then.

Consolidating the move

We know that a few shortcomings remain with hashed repositories. For instance darcs add is noticeably slower on big Hashed repositories: http://bugs.darcs.net/issue1938 . We will try to address these issues by the release of 2.8. We are very interested in knowing whether there are other issues, so please let us know on the bug tracker or by commenting this post.

Okay, we talked about a "un-feature", but Darcs 2.8 will also contain a few new features that will probably please a lot of you. This will be for another blog post very soon.

Patches applied in the last week (51)

Thursday, October 28, 2010

The fifth Darcs hacking sprint took place in Orleans over the weekend of 15-17 October.

We seem to be starting a tradition of sprints coinciding with social movements. Last year, the sprint venue in Vienna was squatted by students protesting university fee reforms. This time we were caught in the French pension reform strikes, which knocked out one of our would-be participants and made another lose a day.

The sprint was small but productive. We had four people attending, Florent Becker (also local organizer), Guillaume Hoffmann, Eric Kow and Reinier Lamers.

Talks and discussions

Scribble Scribble Think Think!

Maintaining Darcs

The day before the sprint, Eric gave a talk to undergraduate and masters students on Free and Open Source Software Projects, in particular the principles that we try to apply within the Darcs team.

Therapy session

We kicked off the sprint with a discussion of some of the challenges that we have been facing in the Darcs community and how we hope to rise to them over the long term.

Code quality - darcs code is a gem buried in big pile of muck. We've been making progress tidying the mess and moving towards a clean, well thought out library... but we still have a long way to go.

Portability - darcs relies on GHC, which takes a long time to build and which simply does not support certain niche platforms.

Usability - for all its power, Darcs has a reputation among its fans for being exceptionally easy to use. While we can be proud of our friendly UI and simple mental model, we need to also recognise the parts of Darcs that make life difficult. Here are three areas we should explore:

Patch annotations would allow Darcs to start tracking a repository history while still allowing for patch reordering. People should be able to ask questions like "who signed off on this patch?", and "when was in pulled into the current repository?"

Short version identifiers would make it easier for users to communicate with each other - "Bob, could you please fetch version 83dc9fa3?"

Better conflict marking and summaries would help maintainers to merge sets of patches from long term branches.

Network effects - Darcs is most useful when many other people are also using Darcs or something compatible.

Unlike Git/Hg/Bzr, Darcs lacks bridges with the other DVCSes. The other three can more or less talk to each other because they have similar models. Darcs is a bit different, so making good bridges can be tricky.

The Darcs community lacks services that facilitate collaboration to the same extent that Github does. We need patch-tag, darcsden and friends to get better still!

One piece of low-hanging fruit to pluck is the ability to host Darcs repositories on servers that lack a Darcs binary. How do we push patches over SFTP without the luxury of a remote Darcs binary?

File formats

We continued the discussion from the darcs-users mailing list on machine-readable formats for the Darcs data and command output. This discussion was tricky because it involves many different parts of Darcs and involves juggling some conflicting goals:

Familiarity: attention to de-facto standards used in the revision control community.

Conceptual integrity: all Darcs formats should work the same way

Extensibility: ability accomodate future requirements

Easy parsing: people should be able to whip up quick little scripts to slice and dice Darcs output

Agnosticism: need a good story for arbitrary bytes because Darcs is fairly agnostic to the content of text files

Transparency: no complicated escaping mechanisms as these tend to fall in rare corner cases and would be easy to get wrong.

Conservatism: the less we change Darcs, the better

Reinier had the idea of bringing this discussion to a whiteboard -- this is why you need hackathons! -- which allowed us to take a more global view of the problem. After much discussion, we reached a conclusion was that we should converge on 4 formats:

High level patch format [SAME] (conceptual integrity, agnosticism, conservatism) - this is a high-level representation of patches which is unique to Darcs. For instance, it can describe file renames and word replacement. We plan to continue using this format whenever we need to represent high-level patch contents.

Line-separated annotate format [NEW] (easy parsing, agnosticism, transparency) - We will deprecate the annotate --xml format, and shift to a line-based one. If there are community standards that exist we'll try to use them as much as possible.

Hashed context file format [NEW] (agnosticism, transparency, conceptual integrity) - we will deprecate the changes --xml format and converge to an extended version of the context file format. New features:

file contents hashes (issue1550)

format version information

is-context-file flag (need deps to be safe to use)

Note that where forced to choose, we have essentially sacrificed the otherwise worthy goals of standards compliance and extensibility.

Hacking

Reinier and Guillaume hacking away

Darcs 2.5

Darcs 2.5 is almost here! The release was delayed for quality control reasons, but after many betas and bug fixes, we think we're ready to ship. Reinier put the finishing touches on our first release candidate.

Infrastructure

Eric made a handful of improvements to the issue tracking infrastructure, improving integration with our darcs repository and darcswatch.

User interface

Eric and Reinier polished off some user interface work:

Removed a confirmation prompt asking you if you really want to record your patch when you choose to edit long comment but make no changes. (undo beats confirmation).

Testing UI regression fix by Adolfo: Darcs was overzealous in warning of about unreachable cache entries.

Improved checking of commands that work on file paths

Pristine cache handling

Guillaume documented much of Darcs pristine cache handling, fixing a darcs repair bug along the way. He

No working directory: towards passive repositories

We want to make it as easy for people to use and host Darcs repositories. In particular, we think it would be great if you could host a Darcs repository on any server, without caring if Darcs is installed there or not. While it is already possible to fetch Darcs repositories from such server, what we now need is the ability topush to such repositories without a remote copy of Darcs.

Working in this direction, Florent implemented a long-requested feature for repositories without a working directory. This is useful for repositories which are only meant to be used for pushing/pulling, where the notion of a working directory is superfluous and makes some Darcs operations harder to implement.

Faster annotate (we'll get there!)

Unfortunately, Benedikt could not join us for the sprint as travel from Zurich to Orleans was disrupted by strikes. Luckily, he was still able to participate over IRC. He ported over his work on the "patch index" optimisation to the latest version of the Darcs code in progress (that's a 6 month leap!) and will continue by exposing the patch index to Darcs commands.

Experience report

Guillaume (right) with a question for Reinier

Our Darcs Weekly News editor attended his first sprint 6 months ago in Zurich, starting work on some ProbablyEasy bugs. It was great to see him again and very encouraging to see how much deeper he was getting into Darcs internals. Let's hear it from Guillaume:

I arrived at the sprint with this bug report in mind, written by a NetBSD user who could not build Darcs on his system. I wondered how easy could it be to write a minimal Darcs client that could only fetch a working copy from a Darcs repository, in a programming language more common than Haskell (Python comes to mind).

Thus began my discovery of the hashed repository format. The most susprising thing I discovered was the lack of documentation: currently someone who wants to write a Darcs client can only count on the existing source code. So I started to document what I understood by asking the other sprinters and looking at the code.

I also documented the Growing Pristine Problem as it was cited as being a low point of the hashed repository format with regards to the old-fashioned format. After understanding why this phenomenon happens, I believe that this is an unavoidable issue when one wants to avoid breakage during simultaneous pushing and getting the same repository. Also, it becomes a problem only in really big repositories.

However, some parts of Darcs could be improved. Darcs could do a better work to handle its pristine.hashed files. For instance, as of now, deleting the pristine.hashed directory leads to an almost dead-end situation since "darcs repair" refuses to work unless a dummy pristine.hashed directory is created. I sent a test case and a fix for this problem.

Missing pristine files are generally not handled graciously by Darcs while their presence is not necessary (albeit very important for speed). As of now, "darcs get" refuses to work when a pristine file is missing, and this has already bit me in the past. I proposed an enhancement of this behaviour. Other local commands that use the pristine files fail if one file is missing, but never tell the user to run darcs repair. I will probably work on these two proposals soon.

The aim is to make Darcs as robust as possible with its current format, and above all to prevent users from being exposed to unhelpful error messages.

Thanks

Thanks to Florent and to the rest of the laboratoire LIFO for hosting the Darcs team this weekend! Hosting sprints is an excellent way to support and to interact with the Darcs community.

The obligatory Jeanne D'arc statue photo

A special shout-out also goes to Yannick Parmentier, a LIFO researcher (and coincidentally Eric's former office mate) who very kindly visited us to take photos and shuttle us back and forth between Orleans and the lab. Merci, Yannick!

Merci, Yannick!

See you next time!

This was a really fun sprint. We hope you can join us next time, hopefully in 6 or so months. In the meantime, check out the flickr tag darcs-2010-10 for more photos from the sprint.

Patches applied in the last week (115)

Saturday, April 24, 2010

News and discussions

darcs 2.4.1 was released, fixing a couple of bugs of version 2.4.0. However, a serious bug under Windows was discovered, so Windows users should still stick to the 2.3.1 version, while 2.4.2 is not out:

Patches applied in the last week (29)

Sunday, March 28, 2010

Updated 2010-03-29 with more photos (thanks, David Anderson!), a small correction and a note about the SFC

The Fourth Darcs Hacking Sprint took place last weekend (19 to 21 March) as part of the Zurich Haskell Hackathon. We had a very productive sprint, a bit of code written, polished off many key discussions, had a little beer and a lot of fun.

Overview

In this sprint, we worked on finishing some performance work for the upcoming Darcs 2.5 release this summer (hashed storage, patch index, global caches, inventory hashing); planning our work for the Darcs 2.6 release next year (smart servers, cache cleanup, darcs rebase) and working with new users of the Darcs library.

Issues resolved

issue643 darcs send -o output - Guillaume Hoffmann

issue1473 annotate command line - Stefan Wehr

issue1456 portable darcs dist - Guillaume Hoffmann

New Darcs Hackers

We're always happy to work with new Darcs developers. At this sprint, we were joined by four new contributors.

Guillaume Hoffmann

Guillaume has been writing our Darcs Weekly News articles for a year now. Over the weekend he got his first taste of Darcs hacking, knocking out three ProbablyEasy bugs (darcs dist internals, darcs send -o UI, darcs apply with gzipped patch bundles). Guillaume reports that he can see himself doing more of this in the future!

Steven Keuchel

Steven worked on a new feature to display the file contents hashed associated with any patch. This makes it easier for third party tools to inspect the patch files behind Darcs.

Stefan Wehr and David Leuschner

Stefan and David mostly worked on the Darcs Patch Manager, but to warm up, they tackled a couple of ProbablyEasy bugs, particularly a bug in darcs annotate that was affecting Redmine

Hacking continued...

Darcs hackers at work (Saturday)Photo taken from David Anderson's Picasa site

Bugfix: Darcs on Windows shares

Salvatore tracked down the Windows regression on 2.4 that make Darcs not work on windows shares.

Performance: Fast darcs annotate

Benedikt Schmidt continued his work on the patch index (formerly known as the filecache). The patch index keeps track of which patches affect which files. This index will bring a big boost to darcs annotate performance, particularly for files which are affected by relative small number of patches.

Performance: Global cache

Luca continued his work on breaking up the global cache ($HOME/.darcs/cache) into buckets for faster access. Working with Reinier and Petr, Luca has developed an approach to migrating from old style caches to the new style bucketed ones. He has also improved the implementation to use hard links, to avoid disk space doubling and to preserve backwards compatibility with prior versions of Darcs.

Windows installer

Salvatore put together a nice Windows installer using the bamse package. It looks like we will be able to use this for the planned Darcs 2.5 release this summer. This work will also open the door to nicer integration with Windows tools, for example, using a bundled Tortoise SSH for better experience working with SSH passphrases.

Interactive cherry picking

Florent improved the quality of the Darcs cherry picking code, making it easier to fine tune our user interface and some day support graphical interfaces via the Darcs library. Witnessed list zippers for the win?

Interactive diff

Florent also started work on adding Darcs's interactive cherry picking to darcs diff, making it possible to choose a set of patches to view as a diff.

Performance: Hashed storage completion

Darcs has a representation of file and directory trees called slurpies. Petr polished off his work to replace the slurpies with his more efficient, general purpose hashed-storage library. Slurpies are going away, and Darcs will be faster for it. He and Ganesh also discussed how to gracefully transition from repositories created before the hashed-storage refactor.

Performance: Using tags when writing patches

Petr ported work by David Roundy to solve a scalability regression in hashed repositories. For darcs commands that write out patches, we had a naive hashing operation that does not account for the fact that patches behind tags cannot be modified. Darcs was unnecessarily traversing the entire sequence of patches (ie. O(n) time) when it could easily have been just traversing the sequence since the last tag.

UTF-8 metadata

Reinier continued to improve the encoding of Darcs patch metadata. Darcs is completely agnonstic with respect to the encoding of your files. Unfortunately, this agnostism extends to patch metadata (patch name, patch author), making it difficult for people to collaborate across different locales. To address this problem, Reinier has been working to make Darcs store its patch metadata in a single encoding (UTF-8) while gracefully supporting older patches (with metadata in potentially any encoding).

Discussions

The rebase discussionAlso from David's site

Release process

The Darcs 2.4 release was quite a tricky one to navigate. We found that bugs were only being flushed out on release candidate time and sometimes after the release proper.

We would like to encourage more people to try out Darcs work in progress and give us feedback early in the release process. After chatting about this, Reinier (with Ganesh, Eric and Petr) decided that as Release Manager, he would put out a Darcs alpha every 4 weeks.

In the future we may investigate automatic nightly builds via the buildbot and a platform support policy such as the one used by Tahoe.

Darcs patch index (fast darcs annotate)

Benedikt updated us on the recent status of his ongoing patch index work (formerly known as the filecache). We discussed the things that make the patch index convincing (permanant, repo-local, unique identifiers for files) the interaction between the patch index and the type witnesses and also ways of tuning the patch index performance and keeping it small.

We're looking forward to sharing the new patch index optimisation with you in upcoming releases. Darcs annotate may become a lot more useful in the next couple of releases!

Readable darcs annotate

Fast darcs annotate won't be useful if nobody can read it. Benedikt and Eric worked on designing a better output format darcs annotate. Taking a page from git blame, there will be one line per source file line, with columns for patch identifier, author name, date and finally the line. One of the design questions was how we should best refer to darcs patches, the current best candidate being a prefix of the darcs patch metadata hash.

Fast darcs over networks

Darcs get over networks is slow, painfully slow. Petr has suggested two priorities for improving the performance of network operations. The first would be to introduce a darcs optimize --http feature which would optimise the Darcs repository for fetching over a network (for example, by creating a "snapshot" of the pristine cache to be fetched in one go). The second priority would be develop a smart server that would provide darcs clients with only the files they need and in the optimal number of chunks. The two ideas combined would make an excellent Google Summer of Code project.

Darcs rebase

Prior to the sprint, Ganesh was working on a darcs rebase feature. Rebase will help Darcs users work with long term branches, and other cases where patch commutation by itself is not enough. At the sprint, Ganesh explained his work to everyone interested. Together we settled on a rough plan for the user interface. It looks like our new rebase command will offer a typically Darcs-ish twist: interactive cherry picking.

Darcs library

Ganesh and Florent talked with three teams building software in the Darcs ecosystem (DPM: Stephan Wehr and David Leuschner, Mac Darcs record GUI: Benedikt Huber and David Markvica, DarcsDen: Alex Suraci). There was a surprising degree of commonality.

The conversations have given us a much stronger sense of direction with the Darcs library. In particular, Ganesh is convinced that we should commit to our use witnesses - at the very least getting them completely finished so we can run with them, probably turning them on by default, and quite possibly dropping the non-witnesses builds.

Default switches

We held a quick roundtable discussion to settle some decisions on Darcs default switches that have been hanging in the air. Our decisions for Darcs 2.5:

--no-set-scripts-executable [unchanged]

pull/push/send --no-set-default

send --edit-description

record --no-test

check --no-test

Performance presentations

Petr and Benedkit gave lighting talks, showing some of our recent performance work to the Haskell community. Some exciting numbers from Benedikt's work (notes) include a 6 second darcs annotate on a file in the GHC repository (previously this did not complete within a half hour).

Google Summer of Code

We discussed our priorities for this year's Google Summer of Code. We have decided that we would focus our attention on performance issues. If we had two GSoC students this year, we would be mainly interested in dividing them between

network performance

developing a smart server for much faster darcs get and pull over a network

We also discussed ways to make the best use of our students' time. The Darcs team has participated in GSoC twice and learning a lot from the experience. This year we would like to see if we could publish some clear guidelines both on what we expect from GSoC students and what they can expect from us. Watch the mailing list for more discussion on this topic.

Budding Ecosystem

We were pleasantly suprised to find ourselves with users of the (still unstable) Darcs API. These new arrivals give us the feeling that the collection of related software is coalescing into a new Darcs ecosystem.

Darcs Patch Manager

David Leuschner and Stefan Wehr worked on an exciting new patch management program for project maintainers. The Darcs Patch Manager (DPM) offers a new way for repository maintainers to keep track of incoming Darcs patches, including their amendements and dependencies.

Towards the end of the hackathon, Stefan gave a nice short demo of DPM in action and deftly avoided the wrath of the demo Gods.

MacOS X GUI for Darcs record

Benedikt Huber and David Markvica started work on a graphical interface to the Darcs record command. One key twist is that they make use of the Darcs API to get the kind of dependency-tracking interactiveness goodness that Darcs offers. Bendedikt and Huber report that they have spent most of the hackathon getting to grips with the library. Darcs type witnesses were very helpful for avoiding errors, but they also impose a steep learning curve.

Darcsden

Alex Suraci and Simon Michael made several improvements to Darcsden, an open source hosting solution (akin to Github and Patch-tag). Some recent changes were Atom feeds, the ability to view forks of your repository and cherry-pick patches from them (work in progress). Darcsden also makes use of the Darcs API.

Darcsden fork viewer

Want to host Darcs Hacking Sprint 2010-10?

The Darcs Team would like to hold hacking sprints twice a year. These sprints are an important occassion for us to hold design discussions, hack some code, train new Darcs hackers and generally bond as a team.

Do you think you can help? Please get in touch with me if you think you may be able to host a group of around 20 Darcs hackers one of these October or November weekends.

Thanks!

Getting over 75 Haskell hackers into Zürich and having them up and running on arrival (Swiss power plugs notwithstanding) was no easy task! We'd like to thank Johan Tibell, David Anderson and the rest of the Google Crew for their hard work organising this hackathon.

Thanks also to the generous donors who chipped into our 2010 Darcs Travel Fund. We'll be looking forward to using the leftover cash for the upcoming 5th Darcs Hacking Sprint in October or November.

Speaking of donors, we'd particularly like to thank the Software Freedom Conservancy for providing us with the infrastructure (both legal and technical) for accepting donations and holding assets such as the darcs.net domain. Meta projects like the SFC are crucial for the success of volunteer-driven open source projects such as Darcs.

Finally here are some words from happy Darcs hackers:

The sprint was a wonderful social occasion, and it was great meeting most of the Darcs hackers, and also seeing other Haskell hackers interested in working in the Darcs ecosystem. I especially enjoyed teaching them how to use our API. -- Florent

The atmosphere was wonderful and I consider the sprint to have been very productive overall. -- Petr

This is coolest thing I ever did -- Luca

See you in half a year!

Participants

We had ten Darcs hackers in Zürich along with four Haskellers using the Darcs API to do awesome things (plus two more on IRC).